To power electronic mobile devices, such as mobile communication devices and personal care devices like shavers, rechargeable batteries are used. To save energy, modern electronic mobile devices are automatically switched into a low-energy mode, sometimes referred to as sleep mode. To wake up the electronic mobile device from the sleep mode, different techniques are used. In case the electronic mobile device comprises a mechanical on/off switch, the device may be woken up by pressing the mechanical switch. Today this method is used by the majority of electronic mobile devices. A well known example is the smartphone.
When using a mechanical switch, the device will not wake up until the user presses the switch. This means the device is not able to respond to the act of picking up the device. Taking into account the fact that the act of picking up a device usually means the user wants to use it, this can be considered to be a disadvantage.
To overcome this issue, the electronic mobile device may have a mechanical motion sensor incorporated in it. The device will then be woken up when the mechanical motion sensor generates a pulse train which meets a predetermined wake-up requirement, e.g. a minimum/maximum duration and frequency. A wake-on-pickup function can be achieved with this approach. In this case it is possible to wake the device by picking it up. However, the device will also be prone to wake up due to random vibrations and shocks, which is undesirable. An existing solution to this problem is to disable the motion sensor for a while when the device has woken up a predefined number of times without user interaction. However, this means the device will be completely unresponsive to motion during that time. Also, in order to ensure that the device remains operable under all circumstances, an alternative method for waking/activating the device needs to be implemented, for example adding a mechanical switch. This leads to additional costs, complexity and less intuitive device operation.
Alternatively, the electronic mobile device may use a capacitive touch sensor. The mobile device can then be woken up when the user touches e.g. a screen or window of the device comprising the capacitive touch sensor. Like in the above implementation of using a mechanical switch, the device will not wake up until the user touches the sensor. This means the device is not able to respond to the act of picking up the device.
A further alternative is the use of an accelerometer within the electronic mobile device. The device will be woken up when a measured acceleration along at least one of the axes of the accelerometer exceeds a threshold (e.g. by shaking, turning or picking up the device with sufficient speed) or when the device is held in a specific orientation. However, when waking up a mobile device based on acceleration exceeding a certain threshold, the device will not always wake up when needed. For example when the device is picked up very (too) slowly, or when the device is not held in the correct orientation.
Patent application WO 2010/042661 discloses a method and system for waking up an electronic mobile device due to motion. The device comprises an accelerometer configured to register a motion of the device. A computation logic analyzes the motion data to determine if the motion data indicates a real motion. If so, the device is woken up. The device comprises a long average logic configured to calculate a long average of accelerations over a sample period along a so-called dominant axis. The sample period may be 5 minutes. The long average logic adds the sampled motion data to a long average value to create an updated long average value of accelerations. The computation logic compares the idle dominant axis with the current dominant axis. If the dominant axis has changed, then the orientation of the device has changed, and that warrants waking up the device. If the dominant axis is substantially the same as the idle dominant axis, then the computation logic determines whether the long average value along the dominant axis has changed by more than a threshold value. If the long average value has changed more than the threshold value, the device is woken up.
A disadvantage of the electronic mobile device described above is that accelerations are very sensitive to shocks and other abnormalities. So, it is necessary to compensate for glitches. In the electronic mobile device known from WO 2010/042661, this compensation is done by adding additional logic such as a glitch correction logic. This will increase the complexity and costs of the device. Furthermore, the use of a long average of accelerations requires additional hardware such as a ring buffer memory, and results in an unwanted additional amount of data processing.
WO 2009/068648 A1 discloses a portable electronic apparatus having first and second display areas. The apparatus has an orientation sensor, that measures a spatial orientation of the apparatus, and a display controller coupled to the orientation sensor. The display controller switches the first and second display areas between a first and a second display state, for example between on and off states, depending on the orientation of the apparatus measured by the orientation sensor. The display controller periodically calculates a movement of the apparatus as the difference between a current orientation measured by the orientation sensor and a previous orientation stored in a memory. If the calculated movement is below a threshold, the display controller does not switch the display areas. If the calculated movement exceeds the threshold, the display controller draws a conclusion about whether or not to switch the display areas based on an analysis of the calculated movement. In case the display controller switches the display areas, the previous orientation in the memory is replaced by the current orientation.
EP 2 703 778 A1 discloses a portable electronic device comprising a display screen which toggles between landscape and portrait orientations based on the orientation of the device. The orientation of the device is determined by a combination of different sensors, i.e. a gyroscope, an accelerometer and a magnetometer. The gyroscope is configured to sense rotational velocity of the device. The device determines a current orientation of the device based on a past reference orientation, stored in a temporary storage, and the rotational velocity measurements of the gyroscope. The past reference orientation is calculated using the measurements of the accelerometer and the magnetometer. The measurements of the accelerometer and the magnetometer are periodically collected in order to provide a corrected reference orientation from which the current orientation of the device can be calculated based on the gyroscope measurements. The periodic correction of the reference orientation is performed in order to limit the drift caused by errors in the gyroscope measurements.